1. Field of the Invention
The present invention relates to a device for broadband data service transmission in a telecommunication system. The invention is aiming at implementation of bridges in public ATM networks (Asynchronous Transmission Mode) by which public data communication services can be used by private, local area networks (LAN). The bridges use a connectionless data service function by means of broadband data service servers BDS (Broadband Data Service). The ATM-network uses the protocol AAL5 (ATM Adaption Layer 5).
2. Discussion of the Background
It is previously known to connect a local network to an ATM network by means of converting units outside the ATM network. Packing and depacking of the information occurs in each node. This requires that the server has a buffer and can maintain many connections at the same time, which causes delays in the system. A number of patent documents are also known within the field.
WO 92/2189 shows an interface for connection of local networks to ISDN (Integrated Services Digital Network). The interface is transparent for a local network user. In order to optimize the use of bandwidth, the packets are packed together to a train of packets which is compressed before it is transmitted.
U.S. Pat. No. 5.229.994 describes a bridge for connection of a local network to an asynchronous telecommunication network. The bridge allows "layer 2.1" for communication with the network.
WO 93/26107 relates to an "ATM-ETHERNET portal/concentrator" which allows transparent connection of Ethernet segment over an ATM network. By using a double port memory the construction becomes simple, the processor power slight and the capacity high, because there is no need to copy data cells.
U.S. Pat. No. 5.179.555 shows a bridge for connecting data traffic between local networks and a WAN (Wide Area Network). Data which are to be transmitted in the WAN is compressed in frames to get high transmission capacity. After each compressed frame, a marker is placed called "end of compression".
EP, A1 0 473 066 relates to a system for connection of local networks to an ATM network. In order to increase the transmission rate for cells from one bridge to another, complete logical connections are, as far as possible, used.
The above documents shows different ways of using bridges for connection of traffic between different networks, for instance local networks and an ATM network. The bridges in the shown documents use different ways in order to, in an efficient way, transfer data packets. None of the documents describe bridges which do not buffer traffic and which makes use of AAL5.